Decimal-dial.



C. E. LATSHAW.

DECIMAL DIAL.

APPLICATION FILED JULY 29,1918.

1 3O 1 1 Patented Apr. 22, 1919.

CHARLES E. LATSHAW, 0F MINNEAPOLIS, MINNESOTA.

DECIMAL-DIAL.

Specification of Letters Patent.

Patented Apr. 22, 1919.

Application filed July 29, 1918. Serial No. 247,341.

To all whom it may concern:

Be it known that 1, CHARLES E. LATSHAW, a citizen of the United States, and a resident of Minneapolis, in the county of Hennepin and State of Minnesota, whose post-office address is 5032-Queen Avenue, South Minneapolis, have invented certain new and useful Improvements in Decimal-Dials, of which the following is a specification.

The object of this invention is to provide a device for instantly locating the decimal point when using any adding, listing, or non-listing machine that is practical for multiplying from left to right.

With this and incidental objects in view, the invention consists of certain novel features of construction and combination of parts, the essential elements of which are hereinafter described with reference to the drawing which accompanies and forms a part of this specification.

In the drawing, Figure 1 is a plan View of a decimal dial embodying my invention, and having a part of the rotating portion broken away to partly show the signal card, Fig. 2 is a section taken on the line 2-2, Fig. 1.

Adding machines were primarily constructed to perform the function of addition, and machines that list the items are generally equipped with a key for repeating. By the use of the repeat key items are duplicated a plural number of times, without rewriting the number on the key board.

This form of addition is termed multiplication. When the multiplier is composed of several digits, the items are repeated the required number of times in the units column. It is then shifted to the tens, hundreds, and thousands column, thus multiplication is speedily accomplished by addition.

The non-listing machine arrives at practically the same result, but in a little different manner. Multiplying from right to left on the adding machine is very limited, unless the machine is of extra large capacity.

One versed in adding machine operation finds it very easy and highly practical to multiply from left to right, and when using whole numbers followed by decimals, problems are found where the roduct is so large that multiplying the pro lem from right to left, the machine is rarely ever large enough to give correct results, where by reversing matters and multiplying from left to right, the product is sufliciently correct for all practical purposes.

The reason for the greater accuracy when multiplying is accomplished from left to right, on an adding machine, rather than from right to left, is apparent to mathematicians, as it is self evident that the right hand numbers, whether decimal or whole numbers, are minute fractions of the entire number, hence if one or more of the right hand digits of the product are dropped the change in the product is immaterial, but naturally if a single left hand digit is dropped the number would greatly decrease in value.

It is not an easy matter to properly and quickly place the decimal when multiplyin from left to right, and to overcome this difiiculty my decimal dial has been designed.

The decimal dial as shown in the drawing will enable the operator to instantly locate a decimal point when using an adding, listing or non-listing machine for multiplying from left to right in a manner now in use and explained in the different instruction books pertaining to various types of machines, none of which, however, give any instructions that would enable the operator to locate the decimal point as is done by the decimal dial. By the use of the dial the operator may locate correctly the decimal point when multiplying integers followed by endless numbers of decimals, or when whole numbers (integers) are found in both the multiplicand and in the multiplier. Whole numbers may be multiplied by decimals or pure decimals by pure decimals.

As shown in the drawing, a base 1 has rotatably mounted thereon by a rivet 2, a disk 3. The base 1 has printed thereon the caption Multiplicand or Multiplier and has the numerals 1 to 9 inclusive spaced above the periphery of the disk in a certain definite relation.

The disk bears on its surface the caption Multiplicand or Multiplier, and has an aperture near its edge with a caption White signal equal number places on one side of the aperture, and on the other side beneath this disk it will display a white signal.

In using the dial to locate the decimal place, first select the first digit to the left of the multiplicand, then select the first digit to the leftof the multiplier. Then locate these two digits, one on the revolving dial, the other on the base and when the digits are solocated turn the dial until'th selected digits are directly opposite, one over the other.

Referring to the small aperture in the dial, the color shown through this aperture will be either red or white. If it is white, point ofi' as many places from the left of the product as there are whole numbers in both the multiplicand and the multiplier; If the color in the aperture is red, point off one less place from left to right of the product than there are whole numbers in both the multiplicand and the multiplier.

The red signal has one exception, and one only, therefore when the red colored signal appears a mental calculation is necessary to ascertainwhether' or not the exception is to be followed on the reading. The white signal, however, has no exceptions.

In the exception, proceed as described heretofore and when two digits'are selected,

say for example 8 and 2, the product is 6. Should this product 6 be greater than the first digit of the product determined on the machine the decimal point is then (in such exceptional cases only) placed the same as if the signal color had been white. In other words Whenever the signal color is red, and the'product of the two digits is greater than the first left digit of the machine product the decimal point is placed the same as though the signal had been white. 7

When multiplying Whole ormixed numbers by decimals the procedure is the same and then move the decimal place one additional place to the left for each cipher pre ceding the first digit of the multiplicand or the multiplier or both. This is largely used in division when the decimal reciprocal of any number (the divisor) is used as the multiplicand and the multiplier is composed of the various digits of the dividend.

When multiplying pure decimals by pure decimals proceed as heretofore described by selecting the first left hand. digits of both the multiplicand and the multiplier regard- 1,so1,14o V less of the number of ciphers that mayv ap pear between the first digits and the decimal point. WVhen this is done and the dial signals white, prefix the first left digit of the product with'as many ciphers as there are ciphers preceding the first digits of the multiplicand and the multiplier, and then place the decimal point to the left of'the last with one additional cipher.- When the ex? ception for the red signal appears proceed the same as in whole numbers, and when it appears the case isv to be treated as though the signal had been white. 3

'F-rom the mechanical description of the device and the directions it is evident that by the peculiar spacing of the numerals on the disk and the arrangement of the colored sector beneath the disk, on the base, with respect to the numerals and the position of the aperture on the disk with respect to the numerals a device is produced that instantaneously enables the operator to locate the decimal point under all conditions of adding machine multiplying, or dividing by decimal reciprocal multiplication.

Claims:

1. As an article of manufacture, a decimal dial comprising a base, and a dial mounted 1 thereon, numerals printed on said base, nu"- merals printed on said dial, co-acting signal means on said dial and base, the relation of saids'ignal means and said numerals being such that by the positioning of one of said numerals on the dial under one of said nume'rals on the base, said signaling means will determine the decimal point location in a product of which the numerals located are the left hand digits of the multiplicand and the multiplier. V

2. In a decimal dial, the combination with a base having digit'sarranged thereon in definite spaced relation, of-a movable member having digits'th'ereon s aced in definite relation, cooperatingsignal means efi'ected by the position of said movable member with said base whereby said signal will, determine whether the decimal point of a product is to be positioned" to the left of the product as many places as there are Whole numbers in both the multiplicand and the multiplier, or whether it will be positioned one less place from left toright than the number of whole numbers in both the multiplicand and multiplier.

3. In a decimal dial, the'c'ombination of a base having digits spaced thereon in definite relation, a dial rotatably mounted on said base and having digits spaced thereon in definite relation, a colored sector on said base under said dial, a signal aperture in said dial for determining the position of a decimal point in a product.

4. In a decimal dial, the combination of a base, a movable member associated with 5 said base, said base carrying thereon spaced in definite relation, the digits 1 to 9 inclusive; said movable member carrying thereon in definite relation the digits 1 to 9 inclusive, and cooperating signal means between said base and said movable member, and adapted to show one of two signals when a digit on said base is alined with a digit 011 said movable member.

CHARLES E. LATSHAW.

Copies of this patent may be obtained for five cents eaoh, by sddressln: the Commissioner of Patents, Washington, D. 0. 

